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Subject: Re: [OMPI devel] IOF redesign: cmd line options
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-08-28 10:00:21

On the various stdout/err options: Other than the complexity of
telling the orteds which procs to do what with, there is nothing
standing in the way of implementing either of those capabilities. I
currently support only sending the info on a per-job basis, though, so
it would mean changing several ORTE-level global object definitions to
store the data, plus changing the launch msg to tell the orteds what
to do. So it wouldn't be a "5-min" kind of job, but it -could- be
done....if someone really, really wanted to.

I have a prototype "orte-iof" tool that does what you describe...will
come into trunk with these changes.


On Aug 28, 2008, at 7:44 AM, Jeff Squyres wrote:

> On Aug 28, 2008, at 6:37 AM, Ralph Castain wrote:
>>>> 1. specify which procs are to receive stdin. The options that
>>>> were to be supported are: all procs, a specific proc, or no
>>>> procs. The default will be rank=0 only. All procs not included
>>>> will have their stdin tied to /dev/null - which means a debugger
>>>> could not attach to the stdin at a later time.
>>> How about: --stdin <list>, where <list> is a comma-delimited list
>>> of integer ranges? Such as:
>>> --stdin 0 (same as default)
>>> --stdin 0,1 (procs 0 and 1 get stdin)
>>> --stdin 0-9 (proc 0 through 9 get stdin)
>>> --stdin 0-9,23-25 (procs 0 through 9 and 23 through 25 get stdin)
>>> --stdin all (all procs get stdin)
>>> --stdin none (no procs get stdin)
>> Just to be clear: is this something that is necessary, or are we
>> providing flexibility that nobody will ever use? Frankly, I'm told
>> that reading stdin at all is pretty rare, at least on jobs around
>> here, though I don't dispute having at least the all, one, or none
>> capability. But is anyone really going to pick-and-choose multiple
>> random procs to receive stdin?
>> I'm asking mostly because of the complexity it adds. Certainly, it
>> is doable - just wondering if it is worth the effort, or something
>> that will never be used.
> Ah -- I actually mis-read your original comment. I'm happy with
> all, none, and X (where X is a single integer).
> "Go for the gold" would be the <list> syntax, but I agree that
> that's not really necessary. I think it's definitely in the "would
> be nice" category.
>>> It occurs to me that we're using this <list> kind of notation in a
>>> few places now (aren't we?). Perhaps we should have this string-
>>> parsing code down in opal somewhere...?
>> Processing it is so trivial it probably doesn't merit a dedicated
>> code - all you do is use opal_argv_split and run down the list.
> I was thinking of the ranges -- there's additional processing for
> the X-Y strings. But it's moot point.
>>>> 2. specify which stdxxx file descriptors you want left open on
>>>> your procs. Our defaults are to leave stdout/stderr/stddiag open
>>>> on all procs. This option would allow the user to specify that we
>>>> tie any or all of these to /dev/null
>>> How about --stdout and --stderr, indicating which procs' stdout/
>>> stderr you want to see? FWIW, I don't think we should provide a
>>> way to turn off stddiag. The syntax could be just like --stdin,
>>> except the default values would be "all".
>> Again, will anyone ever really use this? I agree about stddiag as
>> orte_show_help flows over it. I haven't found any interest around
>> here in shutting off stdout and/or stderr - nobody can think of a
>> reason to do so. Doing it is trivial - my concern here is solely
>> with the complexity of providing such fine-grained specifications.
> It may actually be useful to turn off stdout/stderr in debugging
> scenarios, meaning "I only want to see output from proc X, Y, Z."
> How about leading these options off for now, but leaving the design
> open to implementing them someday if someone ever cares enough?

>>>> Are these options per app context, or global? It would be
>>>> awesome to be per-app-context, but I wouldn't cry too hard if
>>>> they were global (especially if it meant making the code overly
>>>> complex, etc.).
>> My first reaction is that making this per app_context would create
>> a ton of complexity...but I'll take a gander before committing one
>> way or the other. Again, though, I would wonder if anyone really is
>> going to use this on a per app_context basis - or are we just
>> creating capability "because we can"?
> I think it's solidly in the "because we can" department. If it's
> anything more than trivial to implement, my $0.02 is to leave it
> off. If someone wants to implement it someday, they can.
> FWIW: as long as there's the possibility of writing an orte-iof
> command line tool to suck down an individual proc's stdin/stdout/
> stderr[/stddiag], I'm happy (because leaves the door open for
> "mpirun --screen ...").
> --
> Jeff Squyres
> Cisco Systems
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